Heart disease is an umbrella term for several conditions that affect the heart’s structure or function. It is the leading cause of death worldwide, responsible for roughly 19.4 million deaths in 2021, with over 612 million people living with some form of it globally. The most common type in the United States is coronary artery disease, but the term also covers rhythm disorders, valve problems, and heart failure.
Coronary Artery Disease
Coronary artery disease develops when the arteries that supply blood to the heart muscle become narrowed or blocked. The process starts earlier than most people expect. The inner lining of an artery gets damaged by risk factors like high blood pressure, high blood sugar, or high cholesterol. White blood cells move into the artery wall to respond to the damage, and over time, fat, cholesterol, calcium, and cellular debris accumulate into what’s called plaque.
This buildup, known as atherosclerosis, is now understood as a chronic inflammatory process rather than simple cholesterol storage. As plaque grows, it can restrict blood flow to the heart muscle. Heavily narrowed arteries tend to cause chest pain or shortness of breath during physical activity, because the heart can’t get enough oxygen to keep up with demand. But some plaques are more dangerous precisely because they haven’t narrowed the artery much yet. These softer, less stable plaques can rupture suddenly, triggering a blood clot that blocks the artery entirely. That’s a heart attack.
Heart Rhythm Disorders
Your heart relies on a precise electrical system to keep its chambers contracting in the right order and at the right speed. When those electrical signals misfire, the result is an arrhythmia, a heartbeat that’s too fast, too slow, or irregular.
A normal resting heart rate falls between 60 and 100 beats per minute. Bradycardia means the heart beats below 60, which can cause dizziness or fainting if the brain isn’t getting enough blood. Tachycardia means the heart beats above 100 at rest, forcing it to work harder than it should.
Atrial fibrillation is the most common arrhythmia. In this condition, the upper chambers of the heart fire chaotically at rates exceeding 400 beats per minute, though the lower chambers don’t follow at that speed. Because the upper and lower chambers fall out of sync, the heart pumps less efficiently. Atrial fibrillation also raises the risk of blood clots and stroke. On the more dangerous end of the spectrum, ventricular fibrillation causes the lower chambers to quiver instead of pumping. Without treatment within minutes, it’s fatal.
Valve Disease
The heart has four valves that open and close with each beat to keep blood flowing in the right direction. Two main things can go wrong with them. In stenosis, a valve opening becomes too narrow, forcing the heart to pump harder to push blood through. Some people are born with a malformed valve (the aortic valve, for instance, sometimes develops with two flaps instead of the normal three), while others develop stenosis from age-related calcium buildup or prior infections.
In regurgitation, a valve doesn’t seal tightly, allowing blood to leak backward. The most common form involves the mitral valve, where the flaps sag and flop back into the upper chamber. Either problem, if it progresses, makes the heart work harder over time and can eventually lead to heart failure.
Heart Failure
Heart failure doesn’t mean the heart has stopped. It means the heart can no longer pump blood efficiently enough to meet the body’s needs. This can happen after years of coronary artery disease, uncontrolled high blood pressure, valve problems, or damage from a heart attack.
Doctors categorize heart failure by how well the heart still squeezes. A healthy heart pumps out about 55% to 70% of the blood in its main chamber with each beat, a measurement called ejection fraction. Heart failure with reduced ejection fraction means that number has dropped to 40% or below. Some people have heart failure with preserved ejection fraction, where the number stays at 50% or higher but the heart muscle has become stiff and doesn’t fill properly between beats. Both types cause similar symptoms: fatigue, shortness of breath, and fluid buildup in the legs, ankles, or lungs.
Major Risk Factors
Several conditions set the stage for heart disease. High blood pressure tops the list. Normal blood pressure sits below 120/80 mm Hg. Stage 1 hypertension starts at 130/80, and stage 2 at 140/90. The higher your blood pressure, the harder your arteries are being stressed with every heartbeat. High cholesterol contributes directly to plaque buildup. When there’s more cholesterol circulating than your body can use, the excess lodges in artery walls. Diabetes accelerates the process further because elevated blood sugar damages blood vessels and promotes inflammation. Adults with diabetes face a higher risk of dying from heart disease than those without it.
Behavioral factors are equally important. Diets high in saturated fat, trans fat, and sodium raise blood pressure and cholesterol. Physical inactivity increases the risk both directly and by contributing to obesity, high blood pressure, and diabetes. Smoking damages blood vessels, raises blood pressure through nicotine, and reduces the oxygen-carrying capacity of blood through carbon monoxide exposure. Even secondhand smoke raises risk. Excessive alcohol intake raises blood pressure and triglyceride levels.
Symptoms and How They Differ by Sex
Heart disease can be silent for years. Many people don’t know they have it until they experience a heart attack, heart failure symptoms, or a noticeable arrhythmia. When symptoms do appear, they vary depending on the type of heart disease. Coronary artery disease commonly causes chest pressure or pain during exertion, shortness of breath, and fatigue. Arrhythmias may cause palpitations, lightheadedness, or fainting. Heart failure tends to produce swelling in the lower body and difficulty breathing, especially when lying flat.
Women are much more likely than men to have atypical heart attack symptoms. While both sexes can experience classic chest pain, women more often report indigestion, shortness of breath, back pain, nausea, or abdominal discomfort, sometimes without obvious chest discomfort at all. These less recognizable symptoms lead to delays in seeking care and contribute to worse outcomes.
How Heart Disease Is Detected
Diagnosis usually starts with non-invasive tests. An electrocardiogram (ECG) records the heart’s electrical activity and can reveal rhythm problems or signs of a previous heart attack. An echocardiogram uses ultrasound to create a moving image of the heart, showing how well the chambers and valves are working and measuring ejection fraction.
A stress test combines either exercise or medication-induced exertion with monitoring (sometimes including echocardiography) to see how the heart performs under demand. If these tests suggest significant blockages, coronary angiography may follow. This involves threading a thin tube into the heart’s arteries and injecting dye so blockages show up on imaging. It’s both a diagnostic tool and a gateway to treatment, since doctors can open blocked arteries during the same procedure.
Blood pressure checks and cholesterol panels remain the most accessible screening tools. Because heart disease develops gradually and often without symptoms, these routine numbers are frequently the earliest warning sign that something is heading in the wrong direction.